Cognitive function correlates with gastric alpha-synuclein seeding activity in early Parkinson's disease.

Alpha-synuclein (AS) accumulation is more frequently detected in the stomach than in the colon of patients with Parkinson's disease (PD), suggesting its potential as a pathologic biomarker. This study is to evaluate the diagnostic performance of real-time quaking-induced conversion assay on stomach biopsies for early PD and its association with clinical characteristics. Stomach biopsy tissues were prospectively collected from 22 patients with early-stage PD and 17 controls. Pathological AS-seeding activity was assessed, and correlations between kinematic parameters and clinical features were analyzed with age adjustment. Pathological AS-seeding activity was detected in 45.5% of patients with PD and in none of the controls. The Montreal Cognitive Assessment score was correlated with the lag time of positive replicates (Spearman's ρ = 0.742; p = 0.022), after age adjustment. The AS seed amplification assay using the stomach tissue may serve as a biomarker reflecting disease pathophysiology of the gut-brain axis in PD.